例句與造句

1. A sorting method of the helicopter noise sources is given . the temporal waveform and spectrum of the noise signature is analyzed . at last , the sound pressure spectrum density level is estimated with the experimental data taken from a specific navy helicopter
   扼要闡述了直升機(jī)噪聲的產(chǎn)生和分類，考察了直升機(jī)信號(hào)的波形和頻譜特征，并對(duì)特定的直升機(jī)噪聲的聲壓譜密度級(jí)進(jìn)行了計(jì)算。
2. It's difficult to find spectrum density level in a sentence. 用spectrum density level造句挺難的